Internal combustion engines used on agricultural equipment (e.g. mowers) are often exposed to air that contains large quantities of foreign matter. During the normal operation of such engines, a fan draws in air for combustion and cooling purposes through an opening in an engine housing, typically called a "blower housing". Screens are typically placed over the air intake opening to reduce the amount of foreign matter that reaches the engine interior. The screens are typically designed to rotate along with the engine cooling fan so that most of the debris can be shred and shed from the screen, so that air can flow freely through the blower housing.
Even when rotating screens are used, there can still be problems caused by debris accumulating along the inside peripheral surface of the rotating screen. When debris accumulates on the inside peripheral surface of the rotating screen, the air intake inflow area is reduced.
Insufficient air flows and clogging of cooling fins can cause excessively high oil temperature, leading to lubrication quality breakdown (resulting in engine wear). Other problems can also arise, such as reduced horsepower. Compact engines with relatively small air passageways are especially susceptible to the clogging of cooling fins. It is therefore important with engines having a relatively compact cooling system, that passageways be kept as free as possible from debris so they can operate effectively.
There have been some efforts directed at preventing debris from entering the air intake opening around the peripheral edge of the rotating screen. For instance, U.S. Pat. Nos. 5,046,458 and 4,838,908. These systems make it more difficult for debris to enter around the outer peripheral edge of the rotating screen. But, improved performance is desired, especially with respect to debris collecting under the screen near the periphery of the screen.
Another approach is the rotating screen described in U.S. Pat. No. 4,589,379. There, the peripheral edge of the screen is configured to created teeth which rotate outside a rim around the inlet. Debris is cut up into fine particles as it enters the opening in the engine housing. However, the exposed teeth raise some safety concerns and provide no way to correct for wear. Further, it is still desired to reduce the amount of debris collected under the screen.
It can therefore be seen that an improved engine intake screen assembly for alleviating these problems is desired.